Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$174.53	6.517%	$185.9041	$185.90	$185.90	$185.90
Purchase #2	$71.80	13.826%	$81.7271	$81.73	$81.75	$81.70
Purchase #3	$28.28	4.417%	$29.5291	$29.53	$29.55	$29.50
Purchase #4	$65.92	11.577%	$73.5516	$73.55	$73.55	$73.60
Purchase #5	$108.32	13.806%	$123.2747	$123.27	$123.25	$123.30
Purchase #6	$45.46	13.616%	$51.6498	$51.65	$51.65	$51.60
Purchase #7	$137.47	11.814%	$153.7107	$153.71	$153.70	$153.70
7 purchase totals =	$631.78		$699.3471	$699.34	$699.35	$699.30